Last updateTue, 24 Nov 2015 6pm


Power Plant Isolation Valves Beat the Heat

Power Plant Isolation Valves Beat the Heat

About a century ago, pressures of 300 ps...

NACE MR0175/ISO 15156 & NACE MR0103

NACE MR0175/ISO 15156 & NACE MR0103

Q: Is it possible to produce remanufactu...

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Industry Headlines


Industry Headlines

Schlumberger-Cameron Union Receives Unconditional Clearance


Schlumberger Limited and Cameron International Corporation jointly announce that the U.S. Department of Justice has cleared their proposed merger without any conditions, granting early termination of the waiting period required by the Hart-Scott-Rodino Antitrust Improvements Act of 1976 with respect...


ITT Engineered Valves Approved for Star Voluntary Protection Program

ITT Engineered Valves Approved for Star Voluntary Protection Program

ITT Engineered Valves, LLC in Lancaster, PA has been approved by the Occupational Safety and Health Administration (OSHA) of the U.S. Department of Labor for the Star Voluntary Protection Program (VPP).

Approval into VPP is OSHA’s recognition of the exceptional efforts of employers and employ...


Global Petrochemical Prices Leveled Off in October


Prices in the $3-trillion-plus global petrochemicals market in October were virtually flat based on a monthly average, but edged slightly when valued on a month-end to month-end basis from September. This is the first time the markets have shown intermonth gains since May of this year, according to ...


U.S. Rig Count Less Than Half of Last Years Total


According to Baker Hughes, the U.S. rig count declined by 10 last week to 757. Of these 757 active rigs, 564 rigs are seeking oil and 193 are seeking natural gas.

Just a year ago, with oil prices nearly double what they now, there were 1,929 active rigs in the U.S.

The rig count was at its peak in...


Consumer Confidence Falls to 14-Month Low


The Conference Board Consumer Confidence Index, which had decreased moderately in October, declined further in November. The Index now stands at 90.4, down from 99.1 in October. The Present Situation Index decreased from 114.6 last month to 108.1 in November, while the Expectations Index declined to...


Manufacturing PMI Dips to 2-year Low


November data indicated a setback for U.S. manufacturing sector growth, following the modest rebound recorded during the previous month. At 52.6, down from 54.1 in October, the seasonally adjusted Markit Flash U.S. Manufacturing Purchasing Managers’ Index (PMI) pointed to the slowest improveme...


A Case for Mechanical Temperature Control

vmwnt12_beyond_valves_fig1Instrument, mechanical or project engineers may see a multitude of temperature applications cross their desks. Their immediate reaction might be to employ a temperature control loop. But could a mechanical, self-operated temperature regulator be a better solution for the valve application?

When approaching a temperature control application, the engineer usually considers:

  • The degree of accuracy needed
  • Whether the application requires feedback (Are limit switches/output signals used?)
  • Whether the application needs to be controlled through a DCS, PLC or other type of controller
  • The budget for the application.

The answer to whether a mechanical temperature regulator might be a cost-effective and reliable solution for the application depends on those considerations.

In almost any process facility, a variety of temperature control applications can be found. As with any controlled variable, both the accuracy and criticality of those applications can vary widely. Often, non-critical temperature applications become instrumented control loops even when a self-operated or mechanical regulator could provide the desired accuracy along with a substantial cost savings.


vmwnt12_beyond_valves_fig1Figure 1. Temperature regulatorA typical temperature control loop ­(Figure 1) requires:

  • a temperature sensor
  • wiring and conduit
  • connection to a controlling device
  • a control valve (and sometimes a positioner and/or I/P converter, and an air-filter regulator)
  • plant air

A self-contained temperature regulator requires no power, no air supply or other expensive compo­nents to operate. Representative costs based on a 1-inch line size would be:

  • Temperature transmitter: $300-1,000
  • Temperature controller: $400-1,000
  • Control valve and actuator: $1,500-3,000
  • I/P converter: $200-350
  • Air set regulator: $100-150
  • Positioner: $500-2,000
  • Control loop total: $3,000-7,500
  • Temperature regulator: $500-2,500

Although designs may vary from manufacturer to manufacturer, most temperature regulators operate on the same principle. A premeasured amount of “fill” is drawn into the thermal system filling the upper diaphragm chamber, the capillary tube and most of the bulb. As the controlled temperature increases, the fill in the sensing bulb begins to vaporize and creates pressure on the sealed system. This pressure drives the valve stem, closing direct-acting valves or opening reverse-acting valves. By using different fill fluids, many different temperature control ranges can be offered for both cooling and heating applications—temperature ranges are readily available from -20° F (-29° C) to 500° F (260° C).

Applications for which these devices might be ideal include tank farms, large heat exchangers, heat exchangers with slow temperature changes, area heating/cooling (warehouse/maintenance shops) and steam tracing.


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